Issue #574 : remove legacy methods
Issue #574: remove legacy code, change handleNotification to handleRespondedNotifcation, add a place-holder unit test
Issue #574 : implement unit tests for handleRespondedNotification
Issue #574 : code refactoring by using NSString category method of pacoDocumentDirectoryFilePathWithName
Issue #574 : code refactoring by using NSError category method of pacoIsFileNotExistError
Issue #574 : remove legacy code
Issue #218 : code refactor
Issue #218 : fix stop scheduling for experiment, remove legacy code, add a place-holder test